The compounds having an S-sulfate group or an S—SO3−Na+ group were firstly synthesized by Bunte in 1874 and thus are called as “Bunte salts” (cf. H. Bunte, Chem. Ber. 7, 646 (1874)). The Bunte salts are synthesized by the reaction between an alkyl halide and sodium thiosulfate (cf., for example, H. Distler, Angew. Chem. 79, 520 (1967)). This S-sulfate group is oxidized to easily form an S—S bond, but it is relatively stable against air oxidation. While the synthesis of a monomer having an S-sulfate group (cf., for example, German Patent No. 114330: X, Sun, K. Yamauchi, Macromol. Papid. Commun. 22, 401 (2001)) and the polymerization thereof (cf., for example, JP-A-2000-94846: U.S. Patent Laid-Open Publication No. 2003-231236) have been studied, such a polymer is insufficient to be used for a water- and oil-repellent agent.
In addition, vinyl mercaptacetate sodium salt (VMAS) (X, Sun, K. Yamauchi, Marcromol. Rapid. Commun. 22, 401 (2001)) has problems in its low radical polymerizability since it is an unconjugated monomer.
Further, an SH group known as a conventional oxidation crosslinking group is easily oxidized by an air to form an S—S bond, and therefore, the synthesis of an SH group-containing polymer, particularly the production and isolation of said polymer in a solid state have been difficult (cf. K. Yamauchi, Polymer Engineering, 50, 9 (2001)).